/*
 * Copyright (C) 2021 CESNET, https://photonics.cesnet.cz/
 *
 * Written by Tomáš Pecka <tomas.pecka@cesnet.cz>
 *
 */

#include <arpa/inet.h>
#include <linux/if_arp.h>
#include <linux/netdevice.h>
#include "IETFInterfaces.h"
#include "Rtnetlink.h"
#include "utils/log.h"
#include "utils/sysrepo.h"

using namespace std::string_literals;

namespace {

const auto CZECHLIGHT_NETWORK_MODULE_NAME = "czechlight-network"s;
const auto IETF_IP_MODULE_NAME = "ietf-ip"s;
const auto IETF_INTERFACES_MODULE_NAME = "ietf-interfaces"s;
const auto IETF_INTERFACES = "/"s + IETF_INTERFACES_MODULE_NAME + ":interfaces"s;

const auto PHYS_ADDR_BUF_SIZE = 6 * 2 /* 2 chars per 6 bytes in the address */ + 5 /* delimiters (':') between bytes */ + 1 /* \0 */;

std::string operStatusToString(uint8_t operStatus, velia::Log log)
{
    // unfortunately we can't use libnl's rtnl_link_operstate2str, because it creates different strings than the YANG model expects
    switch (operStatus) {
    case IF_OPER_UP:
        return "up";
    case IF_OPER_DOWN:
        return "down";
    case IF_OPER_TESTING:
        return "testing";
    case IF_OPER_DORMANT:
        return "dormant";
    case IF_OPER_NOTPRESENT:
        return "not-present";
    case IF_OPER_LOWERLAYERDOWN:
        return "lower-layer-down";
    case IF_OPER_UNKNOWN:
        return "unknown";
    default:
        log->warn("Encountered unknown operational status {}, using 'unknown'", operStatus);
        return "unknown";
    }
}

std::string arpTypeToString(unsigned int arptype, velia::Log log)
{
    switch (arptype) {
    case ARPHRD_ETHER:
        return "iana-if-type:ethernetCsmacd";
    case ARPHRD_LOOPBACK:
        return "iana-if-type:softwareLoopback";
    case ARPHRD_SIT:
        return "iana-if-type:sixToFour";
    default:
        log->warn("Encountered unknown interface type {}, using 'iana-if-type:other'", arptype);
        return "iana-if-type:other";
    }
}

std::string nlActionToString(int action)
{
    switch (action) {
    case NL_ACT_NEW:
        return "NEW";
    case NL_ACT_DEL:
        return "DEL";
    case NL_ACT_CHANGE:
        return "CHANGE";
    case NL_ACT_UNSPEC:
        return "UNSPEC";
    case NL_ACT_GET:
        return "GET";
    case NL_ACT_SET:
        return "SET";
    default:
        return "<unknown action>";
    }
}

std::string binaddrToString(void* binaddr, int addrFamily)
{
    // any IPv4 address fits into a buffer allocated for an IPv6 address
    static_assert(INET6_ADDRSTRLEN >= INET_ADDRSTRLEN);
    std::array<char, INET6_ADDRSTRLEN> buf;

    if (const char* res = inet_ntop(addrFamily, binaddr, buf.data(), buf.size()); res != nullptr) {
        return res;
    } else {
        throw std::system_error {errno, std::generic_category(), "inet_ntop"};
    }
}

std::string getIPVersion(int addrFamily)
{
    switch (addrFamily) {
    case AF_INET:
        return "ipv4";
    case AF_INET6:
        return "ipv6";
    default:
        throw std::runtime_error("Unexpected address family " + std::to_string(addrFamily));
    }
}

}

namespace velia::system {

IETFInterfaces::IETFInterfaces(std::shared_ptr<::sysrepo::Session> srSess)
    : m_srSession(std::move(srSess))
    , m_log(spdlog::get("system"))
    , m_rtnetlink(std::make_shared<Rtnetlink>(
          [this](rtnl_link* link, int action) { onLinkUpdate(link, action); },
          [this](rtnl_addr* addr, int action) { onAddrUpdate(addr, action); }))
{
    utils::ensureModuleImplemented(m_srSession, IETF_INTERFACES_MODULE_NAME, "2018-02-20");
    utils::ensureModuleImplemented(m_srSession, IETF_IP_MODULE_NAME, "2018-02-22");
    utils::ensureModuleImplemented(m_srSession, CZECHLIGHT_NETWORK_MODULE_NAME, "2021-02-22");
}

void IETFInterfaces::onLinkUpdate(rtnl_link* link, int action)
{
    char* name = rtnl_link_get_name(link);
    m_log->trace("Netlink update on link '{}', action {}", name, nlActionToString(action));

    if (action == NL_ACT_DEL) {
        utils::valuesPush({}, {IETF_INTERFACES + "/interface[name='" + name + "']"}, m_srSession, SR_DS_OPERATIONAL);
    } else if (action == NL_ACT_CHANGE || action == NL_ACT_NEW) {
        std::map<std::string, std::string> values;
        std::vector<std::string> deletePaths;

        auto linkAddr = rtnl_link_get_addr(link);
        std::array<char, PHYS_ADDR_BUF_SIZE> buf;
        if (auto physAddr = nl_addr2str(linkAddr, buf.data(), buf.size()); physAddr != "none"s && nl_addr_get_family(linkAddr) == AF_LLC) { // set physical address if the link has one
            values[IETF_INTERFACES + "/interface[name='" + name + "']/phys-address"] = physAddr;
        } else {
            // delete physical address from sysrepo if not provided by rtnetlink
            // Note: During testing I have noticed that my wireless interface loses a physical address. There were several change callbacks invoked
            // when simply bringing the interface down and up. In some of those, nl_addr2str returned "none".
            deletePaths.push_back({IETF_INTERFACES + "/interface[name='" + name + "']/phys-address"});
        }

        values[IETF_INTERFACES + "/interface[name='" + name + "']/type"] = arpTypeToString(rtnl_link_get_arptype(link), m_log);
        values[IETF_INTERFACES + "/interface[name='" + name + "']/oper-status"] = operStatusToString(rtnl_link_get_operstate(link), m_log);

        utils::valuesPush(values, deletePaths, m_srSession, SR_DS_OPERATIONAL);
    } else {
        m_log->warn("Unhandled cache update action {} ({})", action, nlActionToString(action));
    }
}

void IETFInterfaces::onAddrUpdate(rtnl_addr* addr, int action)
{
    std::unique_ptr<rtnl_link, std::function<void(rtnl_link*)>> link(rtnl_addr_get_link(addr), [](rtnl_link* obj) { nl_object_put(OBJ_CAST(obj)); });

    auto linkName = rtnl_link_get_name(link.get());
    auto addrFamily = rtnl_addr_get_family(addr);
    if (addrFamily != AF_INET && addrFamily != AF_INET6) {
        return;
    }

    m_log->trace("Netlink update on address of link '{}', action {}", linkName, nlActionToString(action));

    auto nlAddr = rtnl_addr_get_local(addr);
    std::string ipAddress = binaddrToString(nl_addr_get_binary_addr(nlAddr), addrFamily); // We don't use libnl's nl_addr2str because it appends a prefix length to the string (e.g. 192.168.0.1/24)
    std::string ipVersion = getIPVersion(addrFamily);

    std::map<std::string, std::string> values;
    std::vector<std::string> deletePaths;
    const auto yangPrefix = IETF_INTERFACES + "/interface[name='" + linkName + "']/ietf-ip:" + ipVersion + "/address[ip='" + ipAddress + "']";

    if (action == NL_ACT_DEL) {
        deletePaths.push_back({yangPrefix});
    } else if (action == NL_ACT_CHANGE || action == NL_ACT_NEW) {
        values[yangPrefix + "/prefix-length"] = std::to_string(rtnl_addr_get_prefixlen(addr));
    } else {
        m_log->warn("Unhandled cache update action {} ({})", action, nlActionToString(action));
    }

    utils::valuesPush(values, deletePaths, m_srSession, SR_DS_OPERATIONAL);
}
}